`AttributeError: 'numpy.float32' object has no attribute 'name'` when trying to modify Zarr V2 `_FillValue`

[norlandrhagen]

Hey @tomwhite,

I'm trying to change the default _FillValue for an Xarray dataset and then write it to Zarr V2. When I call to_zarr, I get: AttributeError: 'numpy.float32' object has no attribute 'name'.

I don't have a reproducer yet, but the variable encoding looks like:

{
  "chunks": {},
  "preferred_chunks": {},
  "compressors": [
    "Zlib(level=1)"
  ],
  "filters": [],
  "shards": None,
  "_FillValue": "-9999.0",
  "dtype": "float32"
}

Any ideas? Sorry in adv if this is a duplicate!

Traceback:

  File "/Users/nrhagen/Documents/carbonplan/OCR/ocr_pyramid/.venv/lib/python3.13/site-packages/xarray/core/duck_array_ops.py"
, line 422, in fillna
    return where(notnull(data), data, other)
  File "/Users/nrhagen/Documents/carbonplan/OCR/ocr_pyramid/.venv/lib/python3.13/site-packages/xarray/core/duck_array_ops.py"
, line 409, in where
    return xp.where(condition, *as_shared_dtype([x, y], xp=xp))
           ~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/nrhagen/Documents/carbonplan/OCR/ocr_pyramid/.venv/lib/python3.13/site-packages/cubed/array_api/searching_functions.py"
, line 105, in where
    return elemwise(nxp.where, condition, x1, x2, dtype=dtype)
  File "/Users/nrhagen/Documents/carbonplan/OCR/ocr_pyramid/.venv/lib/python3.13/site-packages/cubed/core/ops.py"
, line 575, in elemwise
    return blockwise(
        func,
    ...<2 lines>...
        dtype=dtype,
    )
  File "/Users/nrhagen/Documents/carbonplan/OCR/ocr_pyramid/.venv/lib/python3.13/site-packages/cubed/core/ops.py"
, line 302, in blockwise
    chunkss, arrays = unify_chunks(*args)
                      ~~~~~~~~~~~~^^^^^^^
  File "/Users/nrhagen/Documents/carbonplan/OCR/ocr_pyramid/.venv/lib/python3.13/site-packages/cubed/core/ops.py"
, line 1504, in unify_chunks
    nameinds.append((a.name, ind))
                     ^^^^^^
AttributeError: 'numpy.float32' object has no attribute 'name'
Raised while encoding variable 'tasmax' with value <xarray.Variable (y: 512, x: 512)> Size: 1MB
cubed.Array<array-038, shape=(512, 512), dtype=float32, chunks=((256, 256), (256, 256))>
Attributes:
    cell_measures:  area: areacella
    cell_methods:   area: mean time: maximum
    comment:        maximum near-surface (usually, 2 meter) air temperature (...
    history:        2019-05-02T08:38:27Z altered by CMOR: Treated scalar dime...
    long_name:      Daily Maximum Near-Surface Air Temperature
    original_name:  STMX
    standard_name:  air_temperature
    units:          K

[tomwhite]

I'm not sure what's going on here, so if you have more of a reproducer that would be very helpful @norlandrhagen!

#680 is possibly related.